Liquid silicone rubber compositions are employed in molding applications such as injection molding, compression molding, and the like, and are also used in various other applications as adhesives, mold-making materials, sealants, coatings, etc. These liquid silicone rubber compositions are viscous mixtures of crosslinkable liquid silicone polymer, e.g., organopolysiloxane, with a particulate filler, e.g., reinforcing silica. In some cases the compositions prepared for use in the above-mentioned applications have high apparent viscosities due to high filler loadings, or because the filler has a strong capacity to raise the viscosity. It is desirable in the preparation of these high apparent viscosity liquid silicone rubber compositions to carry out mixing so as to obtain the best possible dispersion of the particulate filler being blended into the liquid silicone polymer. Compact apparatuses that efficiently mix liquid and powder are disclosed in Japanese Patent Publication Numbers 53-38828 and 2-2610. These are continuous mixers that contain a rotating disk installed within a casing so as to divide the interior of the casing into upper and lower mixing compartments. Scrapers are also provided on the upper, lower, and side surfaces of the rotating disk in these mixers. However, at high compounding ratios for microparticulate fillers such as fumed silica or carbon black, i.e., at compounding ratios as high as approximately 20%, the mixture takes on a high apparent viscosity and a substantial increase in shear-induced heat generation occurs in the mixers described above. Blending beyond this point is highly problematic, and it also becomes next to impossible to intermix additional ingredients, especially curing agents, without cooling the product mixture. In addition, when the powder is a property-rich metal powder flake such as silver powder, or a metal powder with a low melting or softening point, the metal powder will aggregate and become unusable from a practical standpoint.
The object of the present invention is to provide a liquid-powder continuous mixer and continuous mixing process that generate little shear-induced heating during liquid-powder intermixing even when large amounts of powder are being mixed into the liquid or when a powder is being intermixed that has a strong thickening capacity.